Language change in Alzheimer's Disease (AD) and elderly individuals has been likened to that of patients with Wernicke's type aphasia (WAPH). Indeed, similar surface level manifestations of language change have been described for AD, WAPH and elderly population: The shared features of discourse change include reduced informativity, incoherence, tangentiality, and verbosity. This research seeks explanations for the similar surface disruptions of discourse across four diverse populations: Two neurologically impaired (AD and WAPH) and two normal elderly groups differing in age (55-70; OE 85-95 years). AD and aphasic subjects are of interest because of the converse relations in cognitive and linguistic abilities. The comparison between AD and elderly populations explores whether AD represents behaviorally an accelerated aging process. This research is guided by a discourse model which conceptualizes the complexity of discourse that is realized at multilevels of language and information structures and by various information handling processes. The investigation examines differential disruptions in aspects of informativity, coherence, information handling operations, and on standardized cognitive and linguistic measures. It is hypothesized that changes in informativity and coherence for OE subjects will mimic those observed in AD, however, the underlying mechanisms will differ. For both AD and OE, global organization structures of meaning (macrostructure) will be impaired. Contrastively, AD will manifest impairment in story structure by loss of essential information, whereas story structure will be relatively preserved for OE subjects. Similar to AD and OE, WAPH will show reduction in informativity and impaired coherence. Unlike either OE or AD, WAPH will show preservation of macrostructure and story structure and impairment of microstructures disrupted as a result of linguistic deficits. Theoretically, this research will provide insight into component processes which underlie communicative competence. Empirically, the study will provide valuable comparative data. Clinically, identification of the discourse profiles are necessary for development of diagnostic tools and intervention protocols. This proposed work adds a critical discourse evaluation at the ADRC at UTSWMCD.